As a structure for a cargo compartment for a truck, for example, a so-called gull wing-type cargo compartment is known wherein a floor panel whose base frame is formed from a metal frame material is attached onto a chassis of a truck, portal frames are attached onto the floor panel as well as the central portions of the front and rear portal frames are connected by a center beam, and left and right side walls and ceiling portions are constructed so that they can be rotatably led up.
In such a structure, loading and unloading of freight into and out of the cargo compartment can be performed not only at the rear side of the cargo compartment but also at the left and right sides, thereby improving the workability of the cargo compartment.
A conventional cargo compartment is constructed using a steel and an aluminum material. In a floor panel 306, for example, as shown in FIG. 77, a base frame 304 is formed from steel angles 301 arranged along a longitudinal direction of a truck, steel angles 302 arranged along a transverse direction of the truck and steel angles 303 disposed on both sides. For example, a plywood 305 provided as a floor material is fixed onto the base frame 304 via fasteners such as vises to form a floor panel 306.
A gull wing panel 316, for example, as shown in FIG. 78, has a ceiling portion and a side wall portion. A gull wing panel 316 is constructed by forming a base material 313 by connecting rail materials 311 extending in the longitudinal direction of a truck via rail angles 312 arranged at a predetermined pitch, and attaching aluminum panels 314 and 315 onto the base material 313.
In addition to the above-described structure, as the formation of a cargo compartment for a truck, known are a so-called van-type cargo compartment wherein a floor panel, whose base frame is formed from a metal frame material, is attached onto a chassis of a truck, front and rear portal frames are attached onto the floor panel, and the front and rear portal frames are connected at their upper, left and right portions. Left and right side walls and ceiling portions are constructed from a skin material, a rear door is provided at a rear end portion, a so-called flat body-type cargo compartment, wherein a floor panel whose base frame is formed from a metal frame material, is attached onto a chassis of a truck, and left and right gates and a rear door are attached to the floor panel.
Recently, making large-sized trucks has been accelerated, and a gull wing-type truck having a great total weight such as one of 25 tons (carrying capacity: about 13 tons) has been popularized.
Although the carrying capacity is expected to be increased in order to reduce the cost of transportation of goods, there is a limitation on increasing carrying capacity in the conventional installation using a metal material because the weight due to the installation of a cargo compartment increases. Further, there is a problem in that a member of a conventional cargo compartment is weak against an external force because of many hollow portions. Furthermore, there is a problem that, because increase of strength of various portions of the cargo compartment is required in order to achieve a structure capable of opening and closing, the thickness of the material used increases as the result. Thus, the weight of the material increases and the weight due to the installation of such a cargo compartment increases. Furthermore, when steel or aluminum are used, there may be problems relating to weatherability and corrosion resistance.
As another problem, because one cargo compartment is constructed from many members, a great cost for processing and fabricating it is required, and the cost for installing such a cargo compartment increases.
Recently installation using an FRP in a part of a cargo compartment has been performed. For example, Japanese Patent Application JP-A-HEI 4-166416 proposes a gull wing panel for a cargo compartment of a truck using an FRP. In this publication, a bent plate having a sandwich panel structure is formed by nipping a block core material made from a balsa material with FRP protecting layers, and a gull wing panel is formed by holding the edge portions of the bent plate by channel members.
In this publication, however, although a balsa material is used as a core material, advantage for lightening is small, and further, because a process for connecting the channel members to the edge portions of the formed body via fasteners such as rivets is required, the cost for installation increases.
Further, although an FRP is used, the FRP portion is not a main rigid member of the panel, that is, it is not a portion for mainly taking charge of a rigidity of the whole of the panel, and most of the rigidity and the strength is maintained by the balsa material provided as the core material and/or the channel members provided at the edge portions as frame members. Therefore, the FRP material mainly functions as a surface protecting material. In such a structure, advantage for lightening due to use of an FRP is very small. Further, it is difficult to increase the rigidity and strength of the panel.